Suresh Ponnusami sat back on his porch by the road south of the Indian textile town of Tirupur. He was not rich, but for the owner of a two-acre farm in the backwoods of a developing country he was doing rather well. He had a TV, a car, and a maid to bring him drinks and ensure his traditional white Indian robes were freshly laundered every morning.

The source of his wealth, he said, was a large water reservoir beside his house. And as we chatted, a tanker drew up on the road. The driver dropped a large pipe from his vehicle into the reservoir and began sucking up the contents.

Ponnusami explained: "I no longer grow crops, I farm water. The tankers come about ten times a day. I don't have to do anything except keep my reservoir full." To do that, he had drilled boreholes deep into the rocks beneath his fields, and inserted pumps that brought water to the surface 24 hours a day. He sold every tanker load for about four dollars. "It's a good living, and it's risk-free," he said. "While the water lasts."

A neighbor told me she does the same thing. Water mining was the local industry. But, she said, "every day the water is reducing. We drilled two new boreholes a few weeks ago and one has already failed."

Surely this is madness, I suggested. Why not go back to real farming before the wells run dry? "If everybody did that, it would be well and good," she agreed. "But they don't. We are all trying to make as much money as we can before the water runs out."

Ponnusami and his neighbors were selling water to dyeing and bleaching factories in Tirupur. The factories once got their water from a giant reservoir on southern India's biggest river, the Kaveri (see picture). But the Kaveri was now being pumped dry by farmers and industry farther upstream. The reservoir was nearly empty most of the year. So the factories had taken to buying up underground water from local farmers.

It is a trade that is growing all over India—and all over the world.

Draining Fossil Aquifers

We are used to thinking of water as a renewable resource. However much we waste and abuse it, the rains will come again and the rivers and reservoirs will refill. Except during droughts, this is true for water at the surface. But not underground. As we pump more and more rivers dry, the world is increasingly dependent on subterranean water. That is water stored by nature in the pores of rocks, often for thousands of years, before we began to tap it with our drills and pumps.

We are emptying these giant natural reservoirs far faster than the rains can refill them. The water tables are falling, the wells have to be dug ever deeper, and the pumps must be ever bigger. We are mining water now that should be the birthright of future generations.

In India, the water is being taken for industry, for cities, and especially for agriculture. Once a country of widespread famine, India has seen an agricultural revolution in the past half century. India now produces enough food to feed all its people; the fact that many Indians still go hungry today is an economic and political puzzle, because the country exports rice.

But that may not last. Researchers estimate that a quarter of India's food is irrigated with underground water that nature is not replacing. The revolution is living on borrowed water and borrowed time. Who will feed India when the water runs out?

Nobody knows how much water is buried beneath our feet. But we do know that the reserves are being emptied. The crisis is global and growing, but remains largely out of sight and out of mind.

The latest estimate, published in the journal Water Resources Research this year, is that India alone is pumping out some 46 cubic miles (190 cubic kilometers) of water a year from below ground, while nature is refilling only 29 cubic miles (120 cubic kilometers), a shortfall of 17 cubic miles (70 cubic kilometers) per year. A cubic kilometer is 264.2 billion gallons, or about enough water to fill 400,000 Olympic-size swimming pools.

Close behind India, Pakistan is overpumping by 8.4 cubic miles (35 cubic kilometers), the United States by 7.2 cubic miles (30 cubic kilometers), and China and Iran by 4.8 cubic miles (20 cubic kilometers) each per year. Globally, the shortfall is about 60 cubic miles (250 cubic kilometers) per year, more than three times the rate half a century ago. Egypt, Uzbekistan, Libya, Algeria, Morocco, Syria, Australia, Israel, and others are all pumping up their water at least 50 percent faster than the rains replenish. In some places, water that you could once bring to the surface with a bucket on a short rope is now a mile or more down.

Overwhelmingly, the problem is agriculture. Farming takes two-thirds of all the water we grab from nature, but that figure rises to 90 percent in many of the driest and most water-stressed regions.

This cannot go on, as the United States is already discovering. For more than half a century now, farmers have been pumping out one of the world's greatest underwater reserves, the Ogallala aquifer, which stretches beneath the High Plains from Texas to South Dakota. The pumping began in order to revive the plains after the horrors of the 1930s Dust Bowl. By the 1970s there were 200,000 water wells, supplying more than a third of the U.S.'s irrigated fields.

For a while it was a huge success. In a good year, the High Plains produced three-quarters of the wheat traded on international markets, restocking Russian grain stores and feeding millions of starving Africans. But the Ogallala water is drawing down, many wells are going dry, and the output of the pumps has halved. A quarter of the aquifer is gone in parts of Texas, Oklahoma, and Kansas, and over wide areas the water table has fallen by more than 100 feet.In some places, the sagebrush is returning because farmers are giving up on irrigated planting. (See "That Sinking Feeling About Groundwater in Texas.")

Other countries are heading in the same direction. Water tables are falling by more than a meter a year beneath the North China Plain, the breadbasket of the most populous nation on Earth. Saudi Arabia has almost pumped dry a vast water reserve beneath the desert in just 40 years.

Libya is doing the same beneath the Sahara. Muammar Qaddafi, Libya's late ruler, spent $30 billion of his country's oil revenues on giant pump fields in the desert, and a 2,000-mile (3,200-kilometer) network of pipes to bring underground water that is thousands of years old to coastal farms. Even though it was bombed by NATO forces last year, what Qaddafi called the Great Manmade River Project appears to still be functioning. But nature will eventually accomplish what the bombs did not. Water tables are dropping, pumping is getting harder, and the water is getting saltier.

Soon we may have a full global picture of how the world's underground water reserves are disappearing. Researchers are using NASA's GRACE satellite, which measures changes in the Earth's gravity field, to spot where the pores in rocks are being emptied of water. Jay Famiglietti, an earth science professor at the University of California, Irvine, is analyzing the findings. He says water security will soon rival energy security as the fastest-rising issue on the global geopolitical agenda.

More and more countries are so short of water for farming that they can feed their citizens only by importing crops grown using someone else's water. But the number of countries with spare water to export in this way is diminishing. The fear is that as the world's water supplies run on empty, the world's stomachs will as well.

Often, even before the water runs out, the pumps start to bring up water that is salty or toxic. In parts of India, there are epidemics of fluoride poisoning caused by drinking water containing high levels of this natural compound, which dissolves from hard rocks beneath water-bearing strata. I have seen villages full of severely disabled children, and adults suffering muscle degeneration, organ failure, and cancer caused by these poisons. Some communities call it "the devil's water."

We should not be doing this, says Brian Richter, freshwater strategist at The Nature Conservancy. "Falling groundwater levels are the bellwethers of the unsustainability of our water use," Richter said. "We're raiding our savings accounts with no payback plan."

We should not be stealing water from future generations, Richter said. We should instead use underground water sparingly and with caution.

Seeking Solutions

This can be done, starting with agriculture. Scientists are already working on new varieties of crops that need much less water to grow. And technologists are coming up with less wasteful ways to irrigate those crops. (See "Saving a River, One Farm at a Time.")

The truth is that, despite growing shortages, water is still usually so cheap that it is often wasted. The majority of the world's farmers irrigate simply by flooding their fields. But only a fraction of that water gets absorbed by the plants. Some of it percolates underground and can eventually be pumped to the surface again. But much of it is lost to evaporation.

Even spraying from pivots loses huge amounts of water to the air, where it may get carried out to sea or otherwise lost to local use. So the race is on to develop cheap drip irrigation, in which water is distributed across fields in pipes and dripped into the soil close to plant roots. That way we may be able to save our underground water reserves for future generations.

Meanwhile, communities across the world are running out of water. Where are things worst? The UN Environment Programme (UNEP) nominates the Gaza Strip, the Palestinian enclave on the shores of the Mediterranean between Israel and Egypt. It looks as though it will become the first territory in the world to lose its only water supply.

Gaza has no rivers. It cannot afford desalinated seawater. So its 1.7 million inhabitants drink from the underground reserves. But pumping is being done at three times the recharge rate, water tables are falling fast, and what comes through the wells is increasingly contaminated by seawater seeping into the emptying rocks. A UN report this year said Gaza's water probably will be undrinkable by 2016. What then?

Gaza is an extreme case. And water is only one of its many problems. But it offers a warning for the world. It shows what can happen as the water runs out—what will happen in many other places if we continue to steal water from our children and their children.

Fred Pearce is a journalist and author on environmental science. His books include When the Rivers Run Dry and The Land Grabbers, both for Beacon Press, Boston. He writes regularly for New Scientist magazine, Yale Environment 360, and The Guardian, and has been published by Nature and The Washington Post.

Prior to conceptualizing approaches to sustainably develop and use fresh water sources it is necessary to identify the fresh water source with the greatest potential for sustainable development. Continued use of a fresh water source that is fundamentally impossible to sustainably develop is flawed. Fresh water is scarce. Sensible development and use of the resource is a necessity.

The flow of clean water from taps in the western world creates the illusion of abundance, while, in fact, the small amount of fresh water available on earth is dwindling. The amount of fresh water is so small that all the fresh groundwater on earth can fit in a sphere with a diameter of only 42 miles. Similarly, if one would place the fresh water that instantaneously flow in all rivers on earth in a sphere, it will have a diameter of only 10 miles. A distance of 10 miles is shorter than the daily commuting distance of most people on earth.

Globally humans use three and a half times more groundwater than what is naturally replenished. The non-sustainable use of groundwater is unsettling. This is not the case with river water. In spite of the relatively small amount of fresh water in rivers it has a greater potential for sustainable development than groundwater.

To sustainably develop a renewable resource the rate of usage should be lower than the rate of replenishment. A good proxy for rate of replenishment of surface and groundwater is retention time. The average retention time for groundwater is 1,400 years, while that for river water is 16 to 18 days. In practical terms this means that if one would magically be able to suddenly remove all fresh groundwater on earth in an instant, it will take 1,400 years for it to be replenished. Should we do the same with river water, i.e. suddenly remove all river water on earth it will take little more than two weeks for all of it to return.

So, if we use water on a daily basis the rate of groundwater usage will on average always be significantly greater than its replenishment rate. In the case of river water, one is able to, on average, match the usage and replenishment rates; and create conditions where the usage rate is lower than the replenishment rate. From a global point of view river water has a much greater potential for sustainable development than groundwater. Practical experience bears out this conclusion. Globally groundwater is used at a rate that is 3.5 times greater than its replenishment rate. Contrary to this, although fresh water supply on earth mainly derives from rivers (about 67% of supply) river water is on average not depleted. (Local cases where this happens exist, e.g. the Yellow River; but this is not a global condition).

Globally, the only practical option to sustainably develop fresh water supply systems is to focus on the development of rivers. Admittedly, it requires harmonizing many project development requirements (environmental, social, engineering and economic). But, without finding such solutions, we have no hope to sustainably develop fresh water supply sources; not a rosy prospect for future generations.

George Annandale, Author: Quenching the Thirst: Sustainable Water Supply and Climate Change.

As a former resident of Las Vegas, Nevada, I know about this issue. If it weren't for the city of Las Vegas -with its' tourist trade - this problem wouldn't be nearly the problem it is today.

Make no mistake about it, the people in Las Vegas are seriously worried about their running out of water. Already, the Colorado River's outlet into the Gulf of California has run dry. Eventually, the South West WILL run out of water, unless drastic changes are made to water usage. But, just like the gamblers in Vegas, they won't stop gambling until they are "all tapped out".

You should look into whats being called the SNWA (southern nv water authority) water grab. They have been buying up water rights in Lincoln & white pine counties, very quietly since 1986. They say taking 88,ooo cubic acre feet of groundwater a year will not affect the water table. I know different, many springs run dry in dry or drought years. If they get away w/this it will be the worst environmental disaster in U.S. history. Much worse than Owens valley. They have all the money, the ranchers & others who call eastern NV home have little & will be ruined for generations to come.An investigation by Nat Geo would help I think.If this is not stopped Eastern NV will become an unfamiliar desert. The pinon/juniper/sagebrush roots reach to the top of the groundwater level, if that level drops for an extended period, they will not be able to survive a drought like they normally would. This will destroy whole ecosystems.No more elk,deer,antelope, all the large animals will perish because there are no alternate sources of water,no rivers, large streams ect. It's all spring fed or man made.Hopefully someone who knows someone will read this. Just a little investigating will reveal how sneaky & methodical snwa has been. My grandfather was a rancher, he used to say whiskey is for drinking, water is for fighting. I didn't realize how serious he was.